This invention relates to a hydraulic drive system for a self-propelled turf maintenance equipment unit, such as a riding mower. More particularly, this invention relates to a hydraulic drive system which maximizes the ability of the turf maintenance equipment unit to climb slopes in both forward and reverse.
This invention relates to turf maintenance equipment generally. Riding mowers comprise one type of mower to which this invention relates. Thus, this invention will be explained in the context of riding mowers, but is not limited for use with riding mowers.
Riding mowers are known for use on golf courses and the like for mowing a relatively wide cutting swath, i.e. a cutting swath in the 8xe2x80x2 to 12xe2x80x2 range. Such mowers have a traction frame that is self-propelled by a suitable power source, such as an internal combustion engine, carried on the traction frame. A seated operator is also carried on the traction frame for steering and operating the mower.
Mowers of this type often have multiple cutting units attached to the traction frame. Typically, these cutting units include a front cutting unit and two side cutting units. The cutting units can be either reel-type cutting units or rotary cutting units.
When rotary cutting units are used on the mower, each cutting unit often includes at least two cutting blades rotatably mounted thereon. It is the combination of multiple cutting units, each having multiple cutting blades, that allows a very wide cutting swath to be cut by a rotary mower.
The traction frame often includes a hydraulic traction system having a source of pressurized fluid comprised of one or more hydraulic pumps powered by the engine. The fluid source supplies pressurized fluid to hydraulic drive motors. Certain of these drive motors are operatively connected to at least some of the ground engaging wheels of the traction frame. Other of these drive motors are used to power the cutting units.
Mowers of this type are used on golf courses or similar turf areas, such as parks, which have many slopes. The mower needs to climb such slopes both in forward and reverse. However, previously known hydraulic drive systems did not maximize the ability of the mower to climb slopes in both directions. A mower typically would have good climbing ability when moving up the slope in the forward direction. The same mower would have poor climbing ability when attempting to back up the same slope. This is obviously a disadvantage.
One aspect of this invention relates to a turf maintenance equipment unit which comprises a traction frame capable of movement over the ground. At least one turf maintenance operating unit is coupled to the frame. A hydraulic traction system is provided for powering the traction frame. The traction system comprises a source of pressurized fluid. At least one front drive motor powers at least one front drive wheel on the traction frame. At least one rear drive motor powers at least one rear drive wheel on the traction frame. The front and rear drive motors are connected in parallel to the source of pressurized fluid. A pressure reducing device is provided for supplying the at least one rear drive motor with fluid at different maximum pressures during forward and reverse motions of the traction frame.
Another aspect of this invention relates to a turf maintenance equipment unit which comprises a traction frame capable of movement over the ground. The traction frame has a pair of front drive wheels and at least one rear drive wheel. At least one turf maintenance operating unit is coupled to the frame. A hydraulic traction system is provided for powering the traction frame. The traction system comprises a source of pressurized fluid. At least one front drive motor powers at least one front drive wheel on the traction frame. At least one rear drive motor powers at least one rear drive wheel on the traction frame. The front and rear drive motors are connected in parallel to the source of pressurized fluid. A check valve and pressure reducing device are placed in a fluid path to the at least one rear drive motor and are arranged so that in one direction of motion of the traction frame the fluid leaving the at least one rear drive motor bypasses the pressure reducing device through the check valve and in an opposite direction of motion of the traction frame the fluid entering the at least one rear drive motor is checked by the check valve and passes through the pressure reducing device before entering the at least one rear drive motor.